Vehicular AC generator

ABSTRACT

A vehicular AC generator comprising a pair of cores included in a rotor and supported by a rotating shaft, a plurality of trapezoidal-shaped claws as magnetic poles protruding on the outer periphery edges of the pair of cores, and a pair of fans attached to the front side and the rear side of the cores, at least one of the fans having an outer diameter in the range between 85% and 96% of the outer diameter of each of the cores, each of the claws having a tapered portion for gradually decreasing the outer diameter of a shoulder portion of the claw in the direction toward the end surface of the core so that the outer diameter of at least one of the cores faced to the at least one of the fans becomes substantially the same as the outer diameter of the at least one of the fans, whereby the sound caused by cutting wind by the rotation of the centrifugal fans can be reduced without deteriorating the cooling efficiency of the coil ends of the stator.

This application is a Continuation Application of pending priorapplication Ser. No. 08/835,635 filed Apr. 10, 1997 as a ContinuationApplication of application Ser. No. 08/331,094 filed Oct. 28, 1994 nowabandoned.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a vehicular AC generator having asalient-pole-rotating stator supported by brackets.

(2) Description of the Related Art

A conventional general vehicular AC generator will be described withreference to FIG. 1 to FIG. 4. In the figures, a reference numeral 1represents rear brackets of the generator each having an inlet opening 1a and an outlet opening 1 b. A reference numeral 2 represents arectifier, 3 is a brush holder having a regulator 3 a, and 4 is a rotorconsisting of a pair of cores 4 a 1 and 4 a 2 and is supported and fixedto a rotating shaft 5. A reference symbol 4 b designates a plurality oftrapezoidal-shaped claws functioning as magnetic poles periodicallyprotruding from the edges of the outer peripheries of the cores 4 a 1and 4 a 2. The claws 4 b of the core 4 a 1 and the claws 4 b of the core4 a 2 are alternately arranged in such a way that each of the clawsbelonging to one of the pair of cores is arranged in a concave portionbetween adjacent two of the claws belonging to the other one of the pairof cores. A reference numeral 6 is a coil field accommodated within bothof the cores 4 a 1 and 4 a 2. Reference symbols 7 a and 7 b designatecentrifugal fans respectively attached to the side surfaces of the cores4 a 1 and 4 a 2. Reference numeral 8 represents a stator arranged on theouter periphery of the rotor 4, and consisting of a core 8 a and coilends 8 b and 8 c. Reference numeral 9 is a front bracket having an inletopening 9 a for sucking outside air and an outlet opening 9 b forexhausting air. Reference numerals 10 a and 10 b represent bearings forsupporting the rotating shaft 5.

Next, in the vehicular AC generator constructed as above, a coolingchannel will be described. First, outside air is sucked from the rearbracket 1 through the inlet opening 1 a to cool the rectifier 2 and theregulator 3 a. Then, the cooling air is strongly sucked by thecentrifugal fans 7 a to be bent so as to cool the coil end 8 b of therear side of the stator 8, and is exhausted from the outlet opening 1 b.On the other hand, outside air from the front bracket 9 is flown throughthe inlet opening 9 a and is separated to be flown into two channels,i.e., on one hand, is sucked by the centrifugal fans 7 b to be bent soas to cool the coil end 8 b of the front side of the stator 8 and isexhausted from the outlet opening 1 b, and on the other hand, to coolthe coil field 6 and then is flown to the rear side and is exhaustedfrom the outlet opening 1 b.

In such a general type of the conventional vehicular AC generator, sincethe gap between the outer periphery surface of the shoulder portion ofeach of the claws 4 b and the coil end 8 b or 8 c is small, and sincethe inner surfaces of the coil ends 8 b and 8 c are irregular, there isa problem in that ragged sound caused by cutting wind (interfering soundbetween the coils 4 a 1 and 4 a 2 and the coil ends 8 b and 8 c) isgenerated.

A prior art AC generator to solve such a problem is disclosed in, forexample, Japanese Laid Open Patent Application (Kokai) No. 1-74163/89.This prior art AC generator will be described with reference to FIG. 5.

FIG. 5, the same parts as those in the above-described conventionalgeneral AC generator are denoted by the same reference symbols, and theexplanation thereof are omitted here. Reference numeral 11 designatetapered portions of the outer periphery surfaces of the shoulders of theclaws 4 b each having a sloping surface against the end surface in theshaft direction.

By forming the tapered portions 11 in the claws 4 b as above, the gapbetween each tapered portion 11 of the outer periphery surface of theclaw 4 b and each of the coil ends 8 b and 8 c is gradually increased inthe direction toward the end surface, resulting in that the interferencesound generated, during the rotation of the cores 4 a 1 and 4 a 2,between each of the cores 4 a 1 and 4 a 2 and each of the coil ends 8 band 8 c is reduced.

In the prior art vehicular AC generator shown in FIG. 5, although theinterference noise between each of the cores 4 a 1 and 4 a 2 and each ofthe coil ends 8 b and 8 c can be reduced by the tapered portions 11 inthe outer periphery surfaces of the claws 4 b, however, the gap betweeneach of the centrifugal fans 7 a and 7 b and each of the coil ends 8 band 8 c is still kept to be narrow in order to ensure a coolingefficiency of the coil ends 8 b and 8 c. Because the gap between each ofthe centrifugal fans 7 a and 7 b and each of the coil ends 8 b and 8 cis so narrow, there is a problem in that noise sound caused by cuttingwind is generated between each of the coil ends 8 b and 8 c and each ofthe centrifugal fans 7 a and 7 b during the rotation of the centrifugalfans 7 a and 7 b.

SUMMARY OF THE INVENTION

An object of the present invention is to resolve the above-mentionedproblems, and to provide a vehicular AC generator in which noise soundcaused by cutting wind by the rotation of centrifugal fans can bereduced.

Another object of the present invention is to provide a vehicular ACgenerator in which the cooling efficiency of coil ends of a stator bymeans of the centrifugal fans is not lowered even when the outerdiameters of the centrifugal fans are made small.

Still another object of the present invention is to provide a vehicularAC generator in which noise sound caused by cutting wind by cores can bereduced by making the lowering of the output current due to the decreaseof the outer diameters of centrifugal fans to be smaller.

According to the first aspect of the present invention, there isprovided, for achieving the above object, a vehicular AC generator inwhich at least one of a pair of front and rear fans attached to the bothends of a core of a rotor has a outer diameter in the range between 85%and 96% of an outer diameter of the core.

According to the second aspect of the present invention, there isprovided a vehicular AC generator having a side plate fixed to the endportion of one of the fans and having an outer diameter smaller than theouter diameter of the fan.

According to the third aspect of the present invention, there isprovided a vehicular AC generator in which each of the tapered portionsformed in the claws is provided in at least the front side of thedirection of rotation in the width of the circumferential direction ofeach claw.

As stated above, according to the first aspect of the present invention,since the diameter of the fan is made to be in the range between 85% and96% of the outer diameter of the core, noise caused by the fansthemselves can be reduced, and the sound caused by cutting windgenerated between the fans and the coil ends during the rotation of thefans can be reduced.

Further, according to the second aspect of the present invention, sincethe side plate is attached to the fan, the reduction of the amount ofthe cooling wind due to the decrease of the outer diameter of the fancan be prevented.

Still further, according to the third aspect of the present invention,since each of the tapered portions is provided in at least the frontside of the direction of rotation in the width of the circumferentialdirection of each claw, the lowering of the output current due to thedecrease of the outer diameter of the rotor core can be prevented.

The above and further objects and novel features of the invention willmore fully appear from the following detailed description when the sameis read in connection with the accompanying drawings. It is to beexpressly understood, however, that the drawings are for the purpose ofillustration only and are not intended as a definition of the limits ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing a general vehicular ACgenerator in its shaft direction;

FIG. 2 is a perspective view showing a rotor in FIG. 1;

FIG. 3 is a plan view showing a core in FIG. 2;

FIG. 4 is a perspective view showing a claw of the core shown in FIG. 3;

FIG. 5 is a cross-sectional view showing a prior art vehicular ACgenerator in its shaft direction;

FIG. 6 is a cross-sectional view showing a vehicular AC generator in itsshaft direction, according to a first embodiment of the presentinvention;

FIG. 7 is a perspective view showing a rotor in FIG. 7;

FIG. 8 is a plan view showing a core in FIG. 8;

FIG. 9 is a perspective view showing a claw of the core shown in FIG. 8;

FIG. 10 is a graph showing a result of measurement of wind noise in theembodiment 1 of the present invention;

FIG. 11 is a graph showing a result of measurement of the output in theembodiment 1 of the present invention;

FIG. 12 is a diagram showing the relation between a stator coil and arotor core and a detail size of each portion in the vehicular ACgenerator according to the embodiment 1 of the present invention;

FIG. 13 is a graph showing a comparison of wind noises in the embodiment1 of the present invention and in the prior art example;

FIG. 14 is a cross-sectional view showing a relation between a statorcoil and a rotor core in an embodiment 3 of the present invention;

FIG. 15 is a perspective view showing a claw of the rotor core in FIG.14;

FIG. 16 is a cross-sectional view showing a relation between a statorcoil and a rotor core in the embodiment 4 of the present invention;

FIG. 17 is a perspective view showing a claw of the rotor core in FIG.15;

FIG. 18 is a cross-sectional view showing a relation between a statorcoil and a rotor core in the embodiment 5 of the present invention;

FIG. 19 is a perspective view showing a claw of the rotor core at thefront side in FIG. 18; and

FIG. 20 is a perspective view showing a claw of the rotor core at adifferent front side in the embodiment 5 of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiment 1

An embodiment of the present invention will be described with referenceto FIG. 6 to FIG. 9. FIG. 6 is a cross-sectional view in the shaftdirection; FIG. 7 is a perspective view of a rotor in FIG. 6; FIG. 8 isa plan view of a rotor core in FIG. 7; and FIG. 9 is a perspective viewof a claw of the core in FIG. 8. The same as or the corresponding partsto those in the above-described prior art are denoted by the samereference symbols and the explanations thereof are omitted here.

In the figures, reference symbols 12 a and 12 b are centrifugal fansrespectively attached to the cores 4 a 1 and 4 a 2 of the rotor 4. Theouter diameter of each fan has a size of 92% of the outer diameter ofeach of the cores 4 a 1 and 4 a 2. Reference symbols 13 a and 13 b areside plates fixed to the respective ends of the centrifugal fans 12 aand 12 b. Each of the side plates 13 a and 13 b has a outer diameterequal to or smaller than the outer diameter of each of the centrifugalfans 12 a and 12 b. Reference numeral 14 is a tapered portion formed ata shoulder portion of the claw 4 b of each of the cores 4 a 1 and 4 a 2.The tapered portion 14 is constructed in such a way that the shoulderportion of the claw 4 b is made to have a sloping surface toward the endsurface of the core 4 a 1 or 4 a 2 in its shaft direction so that theouter diameter of the core 4 a 1 or 4 a 2 at its end surface becomes tobe almost the same as the outer diameter of each of the centrifugal fans12 a and 12 b.

In such a vehicular AC generator constructed as above, outside air isflown through a cooling channel from the rear bracket 1 through theinlet opening 1 a to cool the rectifier 2 and the regulator 3 a, andthen the cooling wind is strongly sunk by the centrifugal fan 12 a to bebent at the inner side of the side plate 13 a, and then it cools thecoil end 8 b and is exhausted from the outlet opening 1 b. Since thereis the side plate 13 a, the cooling wind sunk by the centrifugal fan 12a is smoothly bent so that the amount of the cooling wind is notdecreased even though the outer diameter of the centrifugal fan 12 a is92% of the outer diameter of the core 4 a 1.

On the other hand, outside air from the front bracket 9 is flown throughthe inlet opening 9 a and is separated to be flown into two channels,i.e., a one channel through which the air is sucked by the centrifugalfan 12 b to be bent through the inner side of the side plate 13 b so asto cool the coil end 8 c of the front side of the stator 8 and isexhausted from the outlet opening 1 b, and an another channel throughwhich the air cools the coil field 6 and then is flown to the rear sideand is exhausted from the outlet opening 1 b. In this case also, sincethere is the side plate 13 b, the cooling wind sunk by the centrifugalfan 12 b is smoothly bent so that the amount of the cooling wind is notdecreased even though the outer diameter of the centrifugal fan 12 a is92% of the outer diameter of the core 4 a 2.

As described above, the cooling wind can be efficiently flown, and, inaddition, since the outer diameter of each of the centrifugal fans 12 aand 12 b and each of the side plates 13 a and 13 b is made to be thesize of 92% of the outer diameter of each of the cores 4 a 1 and 4 a 2,the noise sound caused by the centrifugal fans 12 a and 12 b themselvescan be reduced. Further, since the gap between each of the centrifugalfans 12 a and 12 b and each of the stator coil ends 8 b and 8 c isexpanded, the sound caused therein by cutting wind can be reduced.

Still further, since the surfaces of the outer peripheries of the claws4 b of the rotor 4 opposite to the stator coil ends 8 b and 8 c are madeto have sloping surfaces so as to form the tapered portions 14 which aretapered toward the respective end surfaces of the rotor 4 in the shaftdirection, the outer diameter of each of the cores 4 a 1 and 4 a 2 attheir end surfaces in the shaft direction becomes almost the same sizeas the outer diameter of each of the centrifugal fans 12 a and 12 b andthe side plates 13 a and 13 b, so that the gap between each of thestator coil ends 8 b and 8 c and each of the tapered portions 14 of theclaws 4 b of the rotor 4 is expanded, resulting in the reduced soundcaused by cutting wind.

Here, the result of measurement of the wind noise and the output in thevehicular AC generator according to the present invention areillustrated in FIG. 10 and FIG. 11. In the measurement, the size of eachportion is set as shown in FIG. 12. The outer diameter (φ91.5) of eachof the side plates 13 a and 13 b and each of the centrifugal fans 12 aand 12 b with respect to the outer diameter (φ100.2) of each of thecores 4 a 1 and 4 a 2 is set to be in the range of 100% to 80%(corresponding to φ100.2 to φ80.16 in FIG. 12), and each measured valueis compared with a reference value which is obtained when the outerdiameter of each of the side plates 13 a and 13 b and each of thecentrifugal fans 12 a and 12 b with respect to the outer diameter ofeach of the cores 4 a 1 and 4 a 2 is set to be 100% (corresponding toφ100.2 in FIG. 12). According to this result, the overall values of thewind noise is gradually decreased when the outer diameter of each of theside plates 13 a and 13 b and each of the centrifugal fans 12 a and 12 bwith respect to the outer diameter of each of the cores 4 a 1 and 4 a 2becomes smaller than 96% (corresponding to φ96.192 in FIG. 12). Theoutput is not largely changed as long as the outer diameter of each ofthe side plates 13 a and 13 b and each of the centrifugal fans 12 a and12 b with respect to the outer diameter of each of the cores 4 a 1 and 4a 2 is in the range between 100% and 85%, however, the output isgradually lowered when it is smaller than 85% (corresponding to φ85.17in FIG. 12). From these results, it is preferable to set the outerdiameter of each of the side plates 13 a and 13 b and each of thecentrifugal fans 12 a and 12 b with respect to the outer diameter ofeach of the cores 4 a 1 and 4 a 2 to be in the range between 96% and 85%(corresponding to φ96.192 to φ85.17 in FIG. 12).

It should be noted that, in FIG. 12, the size of each portion isexpressed by the unit of millimeter. Also, it should be noted that arectangular step (having a height of φ0.75 mm) is formed between theouter diameter (φ100.2 mm) of each of the cores 4 a 1 and 4 a 2 of therotor 4 and the starting point of the sloping surface of each taperedportion 14. By the provision of the step, the life time of the coolforging metal mold of the claws 4 b can be elongated.

The comparison of the overall values of wind noise between the vehicularAC generator of this embodiment and the prior art AC generator is shownin FIG. 13, in which a solid curve represents the embodiment and abroken curve represents the prior art example.

Embodiment 2

In the above-described embodiment 1, the side plates 13 a and 13 b arefixed to the centrifugal fans 12 a and 12 b, however, the side plates 13a and 13 b may be omitted. When the side plates 13 a and 13 b areomitted, the increase in the amount of wind by means of the side plates13 a and 13 b can not be expected, however, in addition to the effect tofurther reduce the noise due to the fans themselves, the effect toreduce the noise generated between the fans and the coil ends when thefans are rotated can be obtained as in the above-described firstembodiment 1.

It should be noted that the centrifugal fan 12 a or 12 b and the sideplate 13 a or 13 b may be provided at one side of the cores 4 a 1 and 4a 2, and the prior art centrifugal fan may be provided at the otherside. In this case, the effect will be reduced to some extent whencompared with the above-described embodiment 1, however, the effectderived from the one centrifugal fan and the side plate is the same asthe effect derived from the one centrifugal fan and the side plate inthe above-described embodiment 1.

Embodiment 3

In the above-described embodiment 1, the tapered portion 14 formed bythe claw 4 b is illustrated as a sloping surface, however, it may be atapered portion 14A formed by a curved surface as illustrated in FIG. 14and FIG. 15.

Embodiment 4

Alternatively, as illustrated in FIG. 16 and FIG. 17, it may be atapered portion 14B formed by two sloping surfaces between which a stepis provided. In this case, since the step in the tapered portion 14Bsuppresses the influence of the magnetic flux, the output current is notlargely lowered so that the noise caused by cutting the wind between thefans and the coil ends can be reduced.

Embodiment 5

In the above-described embodiments 1 to 4, each of the tapered portions14, 14A, and 14B is formed in the full width of the circumferentialwidth of the claw 4 b, however, a tapered portion 14C may be formed inat least front side in the direction of rotation in the circumferentialwidth of the claw 4 b. For example, as illustrated in FIG. 18 and FIG.19, the tapered portion 14C is formed in the front-half portion in thecircumferential width, or as illustrated in FIG. 20, the taperedportions 14C are formed in both the front and the real portions in thewidth in the circumferential direction.

By making the tapered portions 14C as parts of the claw 4 b in thecircumferential width, the decrease in the outer diameters of the rotor4 can be limited, and accordingly, the lowering of the output currentcan be prevented. It is a matter of course that the noise caused bycutting wind between the fans and the coil ends 8 b and 8 c can bereduced due to the presence of the tapered portions 14C. It is also amatter of course that each of the shapes of the surfaces of the taperedportions 14C may be any one of the sloping surface, curved surface, andtwo slope surfaces having a step.

As described above, according to the present invention, since the outerdiameter of the centrifugal fan is made to be smaller than the outerdiameter of the core, there is an effect in that the noise caused bycutting wind during rotating the centrifugal fan can be reduced.

Further, according to the present invention, nevertheless of thedecrease of the outer diameter of the centrifugal fan, there is aneffect in that the cooling efficiency of the coil end of the stator bymeans of the centrifugal fan is not lowered.

Still further, according to the present invention, since the lowering ofthe output current due to the decrease of the outer diameter of thestator core is made to be smaller, there is an effect in that the noisecaused by cutting wind by means of the core can be made small.

What is claimed is:
 1. A vehicular AC generator, comprising: a rotorsupported by a rotating shaft and a stator arranged on an outerperiphery of said rotor, said stator having stator coil ends; a pair ofcores included in said rotor and supported by said rotating shaft, andhaving a plurality of trapezoidal-shaped claws as magnetic polesprotruding on the outer peripheral edges of said pair of cores andalternately arranged in such a way that each of said claws coupled toone of said pair of cores is arranged in a concave portion betweenadjacent said claws coupled to the other of said pair of cores; and apair of fans attached to the front side and the rear side of said cores,at least one of said fans having an outer surface forming an outerdiameter in the range between 85% and 96% of the outer diameter of eachof said cores; each of said claws having a tapered portion for graduallydecreasing the outer diameter of a shoulder portion of said claw in thedirection toward an end surface of said core so that the outer diameterof at least one of said cores facing said at least one of said fansbecomes substantially the same as the outer diameter of said at leastone of said fans and a gap is formed between said at least one of saidfans and a corresponding one of said stator coil ends along acorresponding one of said tapered portions, and wherein the outermostdiameter between the fans is set to be slightly larger than the minimumdiameter between the tapered portions.
 2. A vehicular AC generator asclaimed in claim 1, wherein said tapered portion has a sloped surface.3. A vehicular AC generator as claimed in claim 2, wherein said taperedportion formed in said claw is provided in at least a front side of thedirection of rotation in a circumferential width of said claw.
 4. Avehicular AC generator as claimed in claim 1, wherein said taperedportion has a curved surface.
 5. A vehicular AC generator as claimed inclaim 4, wherein said tapered portion formed in said claw is provided inat least a front side of the direction of rotation in a circumferentialwidth of said claw.
 6. A vehicular AC generator as claimed in claim 1,wherein said tapered portion has two sloped surfaces and a step arrangedbetween said two sloped surfaces.
 7. A vehicular AC generator as claimedin claim 6, wherein said tapered portion formed in said claw is providedin at least a front side of the direction of rotation in acircumferential width of said claw.
 8. A vehicular AC generator asclaimed in claim 1, wherein said tapered portion formed in said claw isprovided in at least a front side of the direction of rotation in thecircumferential width of said claw.
 9. A vehicular A,C generator asclaimed in claim 8, wherein said tapered portion is formed only in saidfront side of the direction of rotation.
 10. A vehicular AC generator asclaimed in claim 8, wherein said tapered portion includes a frontportion formed in said front side of the direction of rotation, and arear portion formed in a rear side of the direction of rotation in acircumferential width of said claw, and a step portion is formed betweensaid front and rear portions.
 11. A vehicular AC generator as claimed inclaim 1, wherein the entirety of the outer diameter is within the rangebetween 85% and 96% of the outer diameter of each of said cores.
 12. Avehicular AC generator as claimed in claim 1, wherein the outer diameterof said at least one of said fans is 92% of the outer diameter of eachof said cores.
 13. A vehicular AC generator as claimed in claim 1,wherein the tapered portion of the claw of the rotor core has a slopedsurface.
 14. A vehicular AC generator as claimed in claim 1, wherein thetapered portion of the claw of the rotor core has one sloped surface,and another sloped surface is provided over the whole circumferentialwidth of the claw.